Transom long or short shaft

[jn626]

I have a 12ft aluminum v-hull with a 16" transom. Can I put a 5hp nissan with a 20" shaft on this boat. I want to be able to use this motor if I get a larger boat. This is my first boat just for back bay fishing and crabbing. Thanks

 

[Joe Reeves]

Re: Transom long or short shaft

JN626.... A 16" transom, measured vertically at the transom center, would be considered designed for a 15" short shaft engine. Your 20" shaft engine will work on that boat but be aware that you will have quite a bit of engine dragging in the water. Also, at high speeds, this drag will create what is usually refered to as a "Rooster Tail" (water shooting up and back from both sides of the engine). In short, there's nothing to keep the engine from operating on that boat, buit it will be impossible for it to operate properly.

 

[Franki]

Re: Transom long or short shaft

Make a bracket to go on your transom, and try to raise it a couple of inches, a long shaft transon us usually about 20 inchs give or take..<br /><br />you have 16, a 2 inch thick piece of box section aluminium bolted to the top of your transom would be a big help.. I have heard a few people on this list suggest that as well.<br /><br />or you can just buy an extension bracket.<br /><br /><br />rgds<br /><br />Frank

 

[Waco]

Re: Transom long or short shaft

I recently raised my transom because I was experiencing the "rooster tail" effect. I haven't been able to test it yet, but heres what I did.

 

[Waco]

Re: Transom long or short shaft

I dont guess that worked either. try this link. http://www.valdosta.edu/~crwillia/boat.htm <br /><br />(I'm having another monday, so if the link doesnt work either, email me. crwillia@valdosta.edu

 

[Waco]

Re: Transom long or short shaft

 

[neurofish]

Re: Transom long or short shaft

I recently put a short shaft 25 on my jonboat (transom made for a short shaft motor). I also deliberated on the long vs short shaft question - where I live used 25 long shafts are a lot easier to find. However, before you build onto your transom remember that torque is force times distance (force = thrust of the motor and distance = the distance from the fulcrom (clamp) to the point of force (propeller)) and that by making the transom higher, you are creating a longer lever arm which will produce more torque. This will place more strain on your transom (welds, bolts, etc.) This is why I held out for a short shaft for mine. Just consider the construction of your boat before you jump into more stress on things that will quickly bring the life of the boat to an end.